1. Field of the Invention
The present invention relates to a transflective liquid crystal display (LCD) panel and a pixel structure thereof, and more particularly, to a transflective LCD panel and a pixel structure thereof having higher aperture ratio.
2. Description of the Prior Art
In manufacturing the LCD, the value of the aperture ratio of the pixel structure directly affects the utilization of the backlight source and the display brightness of the panel. The major factor influencing the aperture ratio of the pixel structure is the distance between a pixel electrode (or transparent conductive electrode) and a data line. If a larger aperture ratio is required, the distance between the pixel electrode and the data line should be shortened. However, when the pixel electrode is too close to the data line, the capacitance between the pixel and data line (Cpd) shall be increased, thereby due to having a different voltage transferred from the data line before the switching to the next frame and thus leading to having the saturated charge on the pixel electrode and resulting in cross talk.
In order to reduce the influence of the Cpd, several methods have been researched. For example, a method is to increase the value of the storage capacitance that can reduce the ratio of the Cpd occupying with respect to all of the capacitors having influence on a sub-pixel unit; in addition, one method is to reduce a parasitic capacitance between the data line and the pixel electrode when there is a stable electrical field shielding between the pixel electrode and the data line; furthermore, a method provided by Optical Imaging Systems (OIS) is to coat an organic insulator film (K=2.7˜3.5) through the use of the photo-imaged and spin on glass (SOG) methods, so that the capacitance between the data line and the pixel electrode can be reduced, so as to allow the pixel electrode to overlap the data line.
However, the above-mentioned methods will result in several negative effects upon the display effect or the fabrication process, so that a further improvement is required. For example, the method of increasing the size and area of the storage capacitor for increasing capacitance shall affect the aperture ratio of the pixel structure. The organic insulator film itself has the issues of water absorption, yellowing, and poor interface adhesion so as to affect the yield and the throughput.
In addition, with regards to the transflective LCD, the standards of some products require a lower reflectivity, such as the reflectivity lower than 3%, which is having the ratio of the size of the reflective region to the total size of the displaying region being lower than 3%. In this situation, it is extremely difficult to design the thin film transistor device and the storage capacitor both inside the reflective region together and to have the thin film transistor device and the storage capacitor being totally shielded by the reflective electrode. The thin film transistor device is an essential device, and thus it cannot be eliminated. If the aperture ratio of the transmissive region is to be totally unaffected, the size of the storage capacitor is required to be reduced. When the storage capacitance becomes too low, an electric leakage issue is easily appeared, and the slightly bright spots or slightly dark spots are generated so as to decrease the quality of the LCD. Therefore, without changing the aperture ratio, the ability to increase the storage capacitance of the transflective LCD is an important subject in the development of the transflective LCD.